1. Field of the Invention
The present invention relates to a keypad and a keypad assembly, and more particularly to a keypad and a keypad assembly including a light guide member having a light guide plate.
2. Description of the Related Art
In general, keypad assemblies are used as information input means for users of personal computers, portable wireless terminals, automatic machinery, etc. Conventional keypad assemblies include a keypad and a switch pad.
The keypad includes a number of key buttons having characters, numerals, and symbols printed thereon, and an elastic sheet having the key buttons fixed to its upper surface. The switch pad includes a printed circuit board (PCB) having a plurality of electric contacts formed thereon, and a dome sheet attached to the PCB.
When a user presses one of the key buttons, pressure is applied to the corresponding dome of the dome sheet via the elastic sheet. Then, the dome is deformed and electrically connected to the corresponding electric contact. Based on the electric connection between the dome and the electric contact, the device (e.g. personal computer, portable wireless terminal, or automatic machinery having the keypad assembly mounted thereon) recognizes that information selected by the user has been inputted.
Keypad assemblies mounted on portable wireless terminals have additional rear lighting means positioned near the key buttons. This enables users to operate the devices even when there is no lighting available.
The rear lighting means come in various types, including: (1) having a plurality of LEDs mounted on the switch pad so as to directly illuminate key buttons, (2) adopting a light emitting structure based on organic light emitting substances, and (3) employing light guide members.
However, conventional rear lighting means have a number of limitations, including that although they are supposed to illuminate key buttons, a considerable amount light is directed to the periphery and then lost. This is an obstacle to making portable terminals that consume less power and that are compact.